As for the preparation of cyclic compounds such as a penem derivative of Formula (8), for example, the method shown in the following reaction scheme has been conventionally known (see, e.g., JP 63-162694 A and JP 6-72875 A):
(wherein R′ represents a t-butyldimethylsilyl group or the like, Z′ represents an acetoxy group or the like, A represents a 5- or 6-membered heteroaliphatic group containing 1 or 2 ring oxygen atoms or the like, R″ represents an allyl group or the like, and R′″ represents an ethyl group or the like).
In the above reaction scheme, however, the step of obtaining a phosphorus ylide compound of Formula (7) from a compound of Formula (6) is actually accomplished by using an excess amount (more than two-fold molar excess) of a trialkyl phosphate represented by the formula (R′″O)3P to react with the compound of Formula (6) for the purpose of improving the reaction yield. Moreover, the reaction mixture is purified using the technique of flash column chromatography before being provided for cyclization to obtain a compound of Formula (8).
However, such technique of flash column chromatography is cumbersome to use when these reactions are performed on an industrial scale, and is also unfavorable in terms of work efficiency. In addition, when the unpurified reaction mixture is directly provided for cyclization, a target product could not be obtained in high yield because structurally unidentified impurities would be by-produced with the target product.
Since the above compound of Formula (8) has more than one asymmetric carbon atom in its molecule and often requires expensive reactants, it is important to obtain a target product in higher yield for its industrially advantageous preparation. Thus, there has been a demand for the development of an industrially advantageous method to prepare a cyclic compound through intramolecular cyclization of a phosphorus ylide compound obtained using a trialkyl phosphite.